A structure, such as a building or a vehicle, commonly includes an envelope defining its boundaries. The envelope separates the structure into an outside (exterior), which is often exposed to sunlight, and an inside (interior), which is often occupied by human beings or other thermal-radiation-emitting items. To keep such a structure at a comfortable temperature, it is typically cooled during the summer and heated during the winter.
Current materials used in the construction of structures are not energy efficient, contributing to increased cooling and/or heating costs through heat gain (during the summer) and/or heat loss (during winter months).
For example, in geographic regions that have colder winters, roofs are often constructed from materials that absorb solar radiation. This type of roof, however, results in excess heat production in the summer, resulting in increased energy costs (to cool buildings) as well as an increase in the local temperatures. To achieve a more energy efficient or even a zero energy building, it is necessary to minimize or eliminate this source of energy loss. Currently, the housing industry provides a thermal insulator between the roof and the internal structure. While somewhat effective, this does not eliminate the excess heat generated by the absorption of sun light in summer days. Similarly, traditional windows are also responsible for energy loss due to heat loss in the winter or heat gain in the summer.
As such, there is a need for an adaptive material which can alter its optical properties depending on the climate. Specifically, there is a need to address methods and materials whereby the thermal loading of conventional envelope materials can be adapted for mixed climate use by providing materials that will absorb sunlight energy during winter months (to help retain heat within a structure) but reflects sunlight during summer months (to help keep the structure cool).